रसायन विज्ञान (Chemistry) – Chemistry MCQ
रसायन विज्ञान (Chemistry) – इन्जिनियरिङ प्रवेश
Chemistry · Engineering Entrance – Mathematics, Physics, Chemistry & English · ७२८ प्रश्न
७२८ प्रश्न उपलब्ध। मोड छान्नुहोस्:
रसायन विज्ञान (Chemistry): प्रश्न र उत्तर
सही लागेको विकल्पमा थिच्नुहोस्। सही भए हरियो, गलत भए रातो देखिन्छ; ३ सेकेन्डपछि सही उत्तर र व्याख्या देखिन्छ।
सही: ० / ०
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At 298 K, the Nernst equation for a cell reaction involving n electrons is:
सही उत्तर: क) E = E° − (0.0591/n) log Q
E = E° − (2.303RT/nF) log Q, and 2.303RT/F = 0.0591 V at 298 K.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The electrode potential of the standard hydrogen electrode is taken as:
सही उत्तर: घ) 0 V
The SHE (H₂ at 1 bar, H⁺ at unit activity) is the reference electrode, assigned 0 V at all temperatures by convention.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the electrolysis of concentrated aqueous sodium chloride (brine) using inert electrodes, the products at the cathode and anode are respectively:
सही उत्तर: ग) H₂ and Cl₂
Water is reduced more easily than Na⁺, giving H₂ at the cathode; at high Cl⁻ concentration Cl₂ is liberated at the anode, leaving NaOH in solution.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a redox reaction, an oxidising agent is a substance that:
सही उत्तर: ख) gains electrons
An oxidising agent oxidises another species by accepting its electrons, and is itself reduced.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The oxidation state of chromium in chromium peroxide, CrO₅, is:
सही उत्तर: क) +6
CrO₅ contains one oxide O (−2) and two peroxide groups (four O at −1): x − 2 − 4 = 0, so x = +6.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A sparingly soluble salt precipitates from solution when:
सही उत्तर: घ) its ionic product exceeds Ksp
Precipitation occurs when the product of the ion concentrations (each raised to its stoichiometric power) exceeds the solubility product.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An aqueous solution of sodium carbonate is:
सही उत्तर: ग) basic
Na₂CO₃ is a salt of a strong base and a weak acid; CO₃²⁻ hydrolyses to give OH⁻ ions, making the solution basic.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The ionic product of water (K_w) on raising the temperature:
सही उत्तर: ख) increases
Self-ionisation of water is endothermic, so K_w increases with temperature (it is 10⁻¹⁴ only at 25 °C).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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According to Ostwald's dilution law, the degree of dissociation of a weak electrolyte:
सही उत्तर: क) increases on dilution
α ≈ √(K_a/C), so as the concentration C decreases (dilution), α increases.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The pOH of an aqueous solution of pH 3 at 25 °C is:
सही उत्तर: घ) 11
At 25 °C, pH + pOH = 14, so pOH = 14 − 3 = 11.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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